Biologics in refractory idiopathic inflammatory myositis (IIM): What experience in juvenile vs adult myositis tells us about the use of biologics in pediatric IIM.

Juvenile dermatomyositis (JDM) is an extremely heterogeneous orphan disease with limited dedicated research. Recent research suggests that JDM, as a type of idiopathic inflammatory myositis (IIM), may not just be the classic antibody driven-complements mediated microangiopathy established in the 1960-2000 decades but also involve inappropriate stimulation of innate immune system followed by dysregulation of the adaptive immune response through dendritic cells. Many variable immune factors such as genetics, major histocompatibility complex expressions, immunohistochemical variabilities, and diversity in specific and associated autoantibodies may make individual IIM and JDM cases unique. The diversity in IIM and JDM also explains individual variability in response to specific therapies. Classifying and matching the right patients to the right treatment is crucial to the successful treatment of these patients with better outcomes. Biologic therapy may be the best current treatment that can match the patient to the best treatment. A PubMed search was performed to find all the available cases of refractory myositis patients treated with biologics up to July 2020. Using this search this article reviews all the current biologic treatment options and experiences for both adults and children in the context of recent basic science to assist pediatric rheumatologists in choosing the optimal biologic therapy for a child with recalcitrant JDM.